“I discussed our assessment, which clearly implicates the Syrian government in this outrage,” Obama said after the meeting. “The prime minister and I are in an agreement that in the face of such barbarism, the international community cannot be silent and that failing to respond to this attack would only increase the risk of more attacks and that possibility that other countries would use these weapons, as well.”

The president said the world set a red line “when governments representing 98 percent of the world’s population said the use of chemical weapons are abhorrent and passed a treaty forbidding their use, even when countries are engaged in war.”

Congress ratified the treaty and strengthened it via the Syria Accountability Act, he said.

The international community’s credibility is on the line in Syria, the president said, and the horrific videos of young children gassed to death require a response. “I do think that we have to act,” he added. “Because if we don’t, we are effectively saying that even though we may condemn it and issue resolutions and so forth and so on, somebody who is not shamed by resolutions can continue to act with impunity, and those international norms begin to erode.”

Other despots will look at a lack of response and believe they can do the same things or worse, the president said.

Obama said he told Reinfeldt that he has high confidence that chemical weapons were used and “that the Assad government, through their chain of command, ordered their use.”

Action can change Bashar Assad’s calculus about using chemical weapons again, Obama said. “We can degrade his capabilities so that he does not use them again,” he added. “What I'm talking about is an action that is limited in time and in scope, targeted at the specific task of degrading his capabilities, and deterring the use of those weapons, again.”